Optical devices and systems are commonly used where manipulation of light is desired. Examples of optical devices include lenses, polarizers, optical filters, antireflection films, optical retarders (e.g., waveplates), and beam splitters (e.g., polarizing and non-polarizing beam splitters). Sub-wavelength structures may be used to control properties of optical beams such as polarization. Articles that are sensitive to the polarization of a beam may include sub-wavelength structure.